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Neurally Adjusted Ventilatory Assist (NAVA)
Sara Connelly, RRT-NPS
**No Disclosures**
Objectives Describe how NAVA works
Explain initiation procedure
Discuss management strategies
What is NAVA?
Mode of ventilation
Requires a Servo I ventilator & a special feeding tube
Can be used with multiple interfaces (invasive or NIV)
Ram Cannula
CPAP/BiPAP mask
Nasal prongs
ETT/trach
NAVA History 1960’s- Diaphragm Electromyography (EMG)
Publications noted increased activity on inhalation with sustained, lower levels on exhalation
1999- Dr. Christer Sinderby invented NAVA
Developed the catheter with electrodes embedded
2000- Collaboration with Maquet
Developed software that eliminates artifact and produces Edi waveform
2007- FDA approval
How does NAVA work?
The Electrical activity of the Diaphragm (Edi) is measured via insertion of a NAVA feeding tube (either NG or OG) and connected to Servo I ventilator.
Clinician sets NAVA level and PEEP
Patient controls their respiratory
rate and tidal volume
The ventilator delivers the breath in
proportion to, and in synchrony with
the Edi signal
Edi signal provides continuous monitoring of the respiratory drive
The signal is measured in microvolts 62.5 times per second
NAVA Concept
NAVAVentilation
Conventional Ventilation
NAVA allows the patient to trigger the ventilator many steps up the neuro-ventilatory cascade providing greater synchrony and patient comfort.
Indications: Contraindications:
Spontaneously breathing Intact phrenic nerve Anticipation of requiring
ventilatory support >48hrs Difficult to wean patients Patients that have ventilator
asynchrony problems unless sedated and/or paralyzed
Past failed extubations Requiring Bipap support
Insufficient/absent respiratory effort
Bilateral diaphragm paralysis secondary to phrenic nerve damage
Central apnea Any contraindications for having
an OG/NG placed or need for MRI Congenital myopathy Esophageal atresia or
diaphragmatic hernia
Edi: The New Respiratory Vital SignEdi Peak:
Represents the signal to the diaphragm during inspiration
Reflective patient’s respiratory status/disease process
Ideally should range from about 10-20 μV
Represents phasic diaphragm activity
Edi Min:
Represents the signal to the diaphragm at end exhalation
Indicative of PEEP optimization
Ideally should range from 0.1-1.0 μV
Represents tonic diaphragm activity
Edi
VT
Health Disease
Neuro-muscular Coupling
μV μV μV
ml ml ml
EDI Catheters Sizes range from 6Fr/49cm to
16Fr/125cm
Lumen for gastric feeding (Sump lumen on 12Fr and 16Fr)
Electrode array (10 electrodes) to measure Edi and esophageal ECG
Coating on Edi Catheter for easier insertion – activated by dipping in sterile water (ONLY use sterile water!)
Barium strip for X-ray identification
Disposable (proper NAVA functionality ensured at least 5 days at normal use although we have been using them for 3-4 weeks without issues)
Normal use for feeding
Are NOT MRI compatible! EDI catheter should be removed, kept as clean as possible and can be reinserted after scan
Edi Catheter Insertion Connect the Edi module and cable Perform the Edi module function check Select appropriately sized catheter Measure NEX (the distance in cm 1-2-3) Access Edi catheter positioning screen
on ventilator Slowly insert catheter to estimated
depth
Edi Catheter PositioningOptimal positioning:
Middle two leads will be highlighted in BLUE
QRS complex decreasing in size from top to bottom
P-waves decreasing in size from top to becoming absent in bottom lead
Document proper position depth
Verify placement per hospital protocol prior to NG use
Edi Catheters
Edi Catheter Positioning
Edi catheter is not inserted deep enough:
Bottom two leads are highlighted in BLUE
Slowly advance catheter until middle two leads are BLUE
Edi Catheter Positioning
Edi catheter is inserted too deep:
Top leads are highlighted in BLUE
Slowly pull catheter back until leads 2 & 3 are BLUE
Monitoring
NAVA PreviewAdjust the NAVA level so that the estimated pressure curve (gray) resembles the actual pressure curve (yellow). The NAVA level is typically set between 1.0 and 4.0 cmH20/μV. The range of settings is 0-15.0 cmH20/μV.
NAVA level x (Edi peak - Edi min) + PEEP = PIP
Invasive Settings Edi Trigg 0.5
Keep PEEP same for now
NAVA level as determined from preview screen
Set appropriate PS settings
Set appropriate backup ventilation settings
NAVA Modes
• Specific cases of asynchrony• Edi Catheter disconnection• ECG signal leakage into Edi signal.
• Edi resp. rate differs from pneumatic resp. rate by less than 20%• 7 of the last 10 breaths are in synchrony with the Edi signal.
• Apnea with low Edi signal and no pneumatic trigger
• Edi signal is back
• No pneumatic trigger
19
© MAQUET
NAVA – NAVA (PS) – NAVA (Backup)
RT will actually set 3 modes for NAVA and the patient will automatically switch between these based upon the criteria below:
*Notify RT if the patient seems to be switching between modesfrequently or is staying in NAVA (Backup).
Invasive NAVA Management Optimize the NAVA level according to Edi peak, which should be
targeted between 10-20 μV.
If Edi peak is < 5 μV, decrease the NAVA level.
If Edi peak is > 25 μV, increase the NAVA level.
Initially, set the same PEEP as in the previous ventilator mode. If Edi min is consistently > 2 μV (as a sign of tonic diaphragmatic activity to maintain FRC), increase PEEP. Optimal Edi min is 0.1-1.0 μV.
When weaning NAVA level, watch for decrease in PIP without loss of Vt.
PIP’s will automatically decrease as the patient's pulmonary status improves.
Troubleshooting
A LOW or absent Edi signal can signify:
Hyperventilation
Sedation
Muscle relaxants
Neural disorder
Catheter malposition
High PEEP levels
A HIGH Edi signal can signify:
Insufficient respiratory support
Pain/Discomfort
Agitation
Non-invasive Settings
Edi Trigg 0.5
Keep PEEP same for now
NAVA level as determined from preview screen
Set appropriate backup ventilation settings
Verify alarm limits (especially PIP and apnea)
Alarms
Upper pressure alarm limit defaults to 20 cmH2O in NIV
Set apnea time for backup ventilation
Non-invasive NAVA Management
The NAVA levels in NIV NAVA are usually lower than in invasive NAVA (0.5 - 1.0 μV/cmH2O).
Higher NAVA levels may increase the amount of gas entering the stomach/intestine and cause abdominal distention.
If Edi peak is < 5 μV, decrease the NAVA level.
If Edi peak is > 25 μV, increase the NAVA level.
The changes in NAVA level should be in steps of 0.1-0.2 μV/cmH2O, with a few breaths between each step.
Usually patients can be switched to nCPAP, when the NAVA level is < 0.5 μV/cmH2O.
The maximum peak pressure is 32 cmH2O, or 5 cmH2O less than set upper pressure limit, whichever is lowest.
WWRTD?
Wean NAVA level due to Edi peak <5 μV
Hint: Optimal Edi peak is 10-20 μV
WWRTD?
Increase PEEP due to Edi min >2 μV
Hint: Optimal Edi min is 0.1-1 μV
WWRTD?
Increase upper pressure alarm limit to ensure you’re not pressure limiting breaths.
Hint: The vent is alarming “regulation pressure limited”
NICU (Invasive NAVA)Arterial Blood Gases Pre/Post NAVA
NAVA Initiated
NICU (Invasive NAVA)Arterial Blood Gases Pre/Post NAVA
NAVA Initiated
“Neurally Adjusted” Ventilatory Assist